Rename Framebuffer::completeness to checkStatus and add an Impl method.

BUG=angle:841

Change-Id: I04b4ffd086424569a15aa21447dd552e0a898928
Reviewed-on: https://chromium-review.googlesource.com/232394
Reviewed-by: Geoff Lang <geofflang@chromium.org>
Tested-by: Geoff Lang <geofflang@chromium.org>
diff --git a/src/libANGLE/Context.cpp b/src/libANGLE/Context.cpp
index fe85831..755b265 100644
--- a/src/libANGLE/Context.cpp
+++ b/src/libANGLE/Context.cpp
@@ -1375,7 +1375,7 @@
 void Context::getCurrentReadFormatType(GLenum *internalFormat, GLenum *format, GLenum *type)
 {
     Framebuffer *framebuffer = mState.getReadFramebuffer();
-    ASSERT(framebuffer && framebuffer->completeness(getData()) == GL_FRAMEBUFFER_COMPLETE);
+    ASSERT(framebuffer && framebuffer->checkStatus(getData()) == GL_FRAMEBUFFER_COMPLETE);
 
     FramebufferAttachment *attachment = framebuffer->getReadColorbuffer();
     ASSERT(attachment);